The present invention relates to a method and apparatus for use in cementing a femoral stem hip prosthesis in the medullary canal of a resected femur and in particular relates to an improved drill bit guide which enables a prosthesis fixture to be attached to the femoral cortex of the resected femur with the use of drill bits or fixation pins passing through the fixture and through the femoral cortex more quickly and accurately than has been done previously.
In U.S. Pat. No. 4,357,716, issued Nov. 9, 1982, there is disclosed a method and apparatus for mounting a femoral stem hip prosthesis in a femoral canal with the use of a cement. Disclosed therein is a prosthesis fixture which mounts the femoral stem of the prosthesis in the femoral canal in a rigid relationship thereto so that the prosthesis stem can be cemented in the canal under pressure while in the rigid relationship to provide a strong bond between the prosthesis stem and the femur. The prosthesis fixture includes a base guide which is generally U-shaped and which has opposing orifices in the legs of the U-shaped guide which are in alignment with each other. These orifices are utilized for a fixation pin or drill bit (hereinafter called "pin") which is driven through the cortex of the femur in order to hold the base guide in a rigid relationship thereto.
These orifices are made only slightly larger than the pins which are used and it has been found that if there is any slight migration of the pin as it passes through the femoral cortex it may not precisely line up with the orifice on the opposite side of the U-shaped guide. This causes the pin to strike the guide itself instead of the orifices thereby requiring the pin to be reset. This not only requires the pin to be re-aligned but of course also increases the required time for the surgery.
In commonly owned co-pending application Ser. No. 734,559, filed May 16, 1986 and entitled IMPROVED DEVICE AND METHOD FOR CEMENTING A HIP PROSTHESIS IN A FEMORAL CANAL, an improvement in the method and apparatus for driving the pins through the base guide was disclosed. A first orifice was provided in one side of the guide for inserting a pin and a second orifice was was inserted in another side of the guide which is much larger in cross-section than the pin. An easily penetrable material such as a cylindrical plastic plug was inserted in the second orifice wherein the pin, in passing through the first orifice and the femoral cortex, could deviate from axial alignment and still strike the plastic plug in the receiving orifice and pass therethrough. Thus the metal frame of the base guide is not touched and yet the pin may deviate somewhat from axial alignment and still penetrate the plastic plug. The plastic plug is threaded and so is the second receiving orifice in which it is inserted so that after the base guide has been used in one operation, the plastic plug can be threadably removed and a new one threadably inserted so that the guide can be used again in the next operation.
Obviously, these prior art methods require excessive amounts of time to insert the Kirschner wires or pins or drill bits if the pins or bits tend to migrate when they reach the cortical bone surface. Of course where the plastic plug is used, the plug must be removed and replaced as needed. Further, if for any reason it is required that the pins or the drill bits be removed and then replaced, the orifices which were formed with a migrating drill bit may not be aligned and thus it may not be possible to re-insert the pins or bits without drilling new orifices.
To overcome the disadvantages of the prior art, applicant provides bit guides which enable the surgeon to drill the orifices more quickly and more accurately than can be accomplished with the prior art methods and apparatus. The improved guide establishes a drill bit path through one leg of the U-shaped base guide, the femoral cortex and the other leg of the U-shaped guide. Thus, a drill bit sleeve is mounted in each orifice in the legs of the U-shaped base guide for guiding the drill bit inserted in the sleeve through the cortex of the femur. The bit sleeves comprise a hollow tube snugly but movably mounted in each of the orifices in the legs of the U-shaped base guide for movement toward and away from the femoral cortex. This enables the sleeve to be moved inwardly and pressed against the femoral cortex thus guiding the drill bit and holding it firmly at the surface of the bone where migration of the bit could occur. Thus migration of the bit is prevented by the bit sleeve and is caused to pass through the cortical bone in a straight line. A shoulder is formed on the outer end of the hollow tube for limiting inward movement of the sleeve toward the cortex and a countersunk opening is formed in each end of the hollow tube for guiding a received drill bit into the hollow bit sleeve.
In addition, once the drill bit has passed through the cortical bone into the medullary canal, it again encounters cortical bone on the opposite side of the medullary canal and again, the drill bit may have a tendency to migrate. Thus the present invention provides for an annular body member for receiving the prosthesis stem and forming a drill bit guide for insertion in the medullary canal. The annular body is rigidly attached to the fixture holding the prosthesis. Passageways extend through the medullary body member in alignment with the opposed orifices in the legs of the U-shaped base guide and thus each receives a drill bit as it passes from the bit sleeve in an orifice in the leg of the U-shaped base guide. The annular body member may be a one piece member having a continuous wall and has a shape comparable to the shape of the periphery of the medullary canal. Thus the passageways provide a guide for the drill bit as it attempts to penetrate the cortical bone on the other side of the medullary canal. Each of the passageways in the annular body member have a countersunk opening at each end thereof for guiding a received drill bit into the passageway.
Thus it is an object of the present invention to provide bit sleeves in the orifices of the base guide to keep the drill bit in a fixed, predetermined path through the cortical bone of the femur and prevent deviation of the bit from a straight path.
It is also an object of the present invention to use a bit sleeve in the orifices of the prosthesis fixture which are snugly but movably mounted in each of the orifices for movement toward and away from the femoral cortex such that they can be moved against the cortical bone to prevent migration of the drill bit as it attempts to penetrate the cortical bone.
It is also an object of the present invention to provide an annular body member as a drill bit guide which is inserted in the medullary canal to establish a drill bit travel path through the medullary canal from the cortical bone on one side of the canal to the cortical bone on the other side of the canal.
It is yet another object of the present invention to provide an annular body member as a bit guide for insertion in the medullary canal between the two cortises of bone.
It is still another object of the present invention to provide an annular body as a drill bit guide having passageways extending through the body member in alignment with opposed orifices i the legs of the U-shaped base guide for receiving and guiding the drill bits through the cortical bone.